Method of constructing electric switches.



- No. 7|2,535. "Patented Nov. 4. I902.

a. H. HILL. METHOD 0F CCNSTRUCTING ELECTRIC SWITCHES.

(Appliqation filed. Jain. 24, 19132.) (No Modem By. J

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GEORGE I-I. HILL, OF GLENRIDGE, NEW JERSEY, ASSIGNOR TO SPRAGUE ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

METHOD OF CONSTRUCTING'ELECTRlC SWITCHES.

SPECIFICATION forming part of Letters Patent No. 712,535, dated November 1902.

Original application filed August 10, 1901, Serial No. 71,640. Divided and this application filed January 24,1902. Serial No. 91,057. (No model.)

i To ctZZ whom it may concern:

Be it known that I, GEORGE II. HILL, a citizen of the United States of America, and a division.

resident of Glenridge, in the county of Essex and State of New J ersey,have invented certain new and useful Improvements in Methods of Constructing Electric Switches, of which the following is a specification.

This invention relates to a method of constructing electric switches, particularly switches of the cylindrical type, in which spider-castings on the shaft are insulated therefrom by an insulating compound, as shown in my copending application, filed August 10, 1901, Serial No. 71,640, and of which'this is a Heretofore the segments or castings have been painted after they have been assembled on the shaft, in such a way that whenever dust, oil, and dirt accumulated on the surface of the compound between the castings a leak of current occurred between them. In a short time a heavy arc would form, with the consequent burning out of the switch. Also as the coat of paint furnishes a film or skin over dissimilar substancesnamely, the castings and the compound it is apt to crack, and thus give opportunity for an initial leak.

The object of the present invention is to provide a method of constructing electric switches by which the insulation is made more effective and these defects avoided; andthe' invention therefore consists of certain novelfeatures to be hereinafter described in detail and then pointed out in the claims.

In the accompanying drawings, Figure l is a side elevation of so much of a switch con structed in accordance with the present inventionassufficestoillustratethesame. Fig. 2 is a section on line 2 2 of Fig. 1, the brushes being omitted; and Fig. 3 is a section on line 3 3 of Fig. 1.

The shaft or spindle A of the switch, here shown as of the cylinder type, is covered with an insulating compoundB, so as to form a layer under and between the castings or segments C, the lugs C of which carry the copper contacts D. The brushes are lettered D.

stance.

The well-known way of applying the insulating compound and castings to the shaft is -to string a number of rings of suitable insuare forced on the shaft, spas to squeeze the softened and now plastic material up into the interstices between the castings, and the process is continued until all of the interstices are filled with the compound, when the structure is allowed to cool off, and the exposed surfaces of the insulation and the castings are then covered with a coat or coats of paint.

In the present invention the described method of assembling is also preferably used; but beforeassembling thecastings C are onameled or japanned with some suitable insulating material Esuch as porcelain, for in- This enamel or japan is hard and baked on the castings, so that it will resist the subsequent heating at the'time the insulating compound is applied to the shaft.

The enamel or japan also provides a hard insulating-skin on the castings which is not readily broken down, and thus prevents the initial leak between the castings, and consequently the disastrous arcing which follows. A coat of. paint F may or may not be applied to the exposed surfaces of the insulation and castings, as heretofore, as shown in Figs. 2 and 3.

The painting of the castings after they have been assembled upon the shaft is not as advantageous as previous enameling or japanning, for the reasons that the paint cannot be hard-baked on account of the lowtemperature limit of the insulating compound, and is therefore not as durable, and also that the paint is liable to crack.

What I claim as new, and desire to secure by Letters Patent', is-

In the heroin described method of con- Signed by me at New York, N. Y., this 22d day of January, 1902.

GEORGE H. HILL.

Witnesses:

GEO. L. WHEELOCK, SAMUEL W. BALOH.

5 an insulating compound over the skin or film covered portion of the support, substantially as described. 

